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Galaxy Clusters as Cosmic Probes

Galaxy Clusters as Cosmic Probes. Subha Majumdar. Pre WMAP - 1999 Science article Bahcall, Ostriker, Steinhardt. Cluster Cosmology - A flavour of decades old results. In this era of CMB, SNe, etc Why do we need clusters?.

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Galaxy Clusters as Cosmic Probes

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  1. Galaxy ClustersasCosmic Probes Subha Majumdar

  2. Pre WMAP - 1999 Science article Bahcall, Ostriker, Steinhardt Cluster Cosmology - A flavour of decades old results DTP Colloquium, TIFR, 29 June 2010

  3. DTP Colloquium, TIFR, 29 June 2010

  4. In this era of CMB, SNe, etc Why do we need clusters? LSST forecast: Strengths of different approaches within one single survey DTP Colloquium, TIFR, 29 June 2010

  5. Cluster surveys / observational programs (incomplete list) Red Sequence Cluster Survey (RCS) Spitzer Adaptation of the RCS (SpARCS) Spitzer Legacy Extremeley Wide Survey (SLEWS) Gemini Cluster Astrophysics Spectroscopic Survey (GCLASS) South Pole Telescope (SPT) APEX-SZ Atacama Cosmology Telescope (ACT) Blanco Cosmology Survey Sunyaev-Zeldovich Array (SZA) ROSAT XMM-LSS Serendipitous Survey XMM-Cluster Survey Pan-Starrs Dark Energy Survey (DES) Hyper SuprimeCam (HSC) Large Synoptic Survey Telescope (LSST) eROSITA, Wide Field Xray Telescope AMIBA, SuZIE, Cluster Imaging Experiment, Cluster Cosmology Atacama Telescope DTP Colloquium, TIFR, 29 June 2010

  6. South Pole Telescope papers are rolling in… 6+1 paper since June 2009 Results are full of surprises!! DTP Colloquium, TIFR, 29 June 2010

  7. Atacama Cosmology Telescope papers are not behind… DTP Colloquium, TIFR, 29 June 2010

  8. What are clusters?How do they form?What do they contain?ANDHow are they distributed? DTP Colloquium, TIFR, 29 June 2010

  9. The WMAP Sky DTP Colloquium, TIFR, 29 June 2010

  10. DTP Colloquium, TIFR, 29 June 2010

  11. Counting clusters: mass function, growth fn & 8: Universality when written in terms M Seth-Tormen: ellipsoidal collapse & Nbody Jenkins etal, bestfit to simulations Also Warren etal, Lukic etal latest. [8 for R=8h-1 Mpc]

  12. Cosmology with Cluster Number Counts(with apologies to)1. with Xray luminosity function2. Xray temperature function3. Xray gas mass fraction4. Optical/Xray cluster 3D corr fn5. Optical/Xray 2D angular correlations6. SZ+XR method of Hubble Const DTP Colloquium, TIFR, 29 June 2010

  13. Cosmology affects cluster counts - DTP Colloquium, TIFR, 29 June 2010

  14. Almost 10 years back…Weller, Battye & Kneissi 2002 Fixed Mlim --> so NO uncertainty in cluster physics --> unrealistic , good as first attempt. Ncl = 13600 SNAP Ncl = 5200 Ncl = 1972 Ncl =90

  15. Chandra Image of Zw38 Problem is we have to deal with real clusters! Large peak in matter density • Dark matter clump (~80% of mass) • Many luminous galaxies (~2%: 10% of baryons) • BCG and red sequence • Additional galaxies • Diffuse light • Hot gas (~18%: 90% of baryons) • Emits X-rays • Causes SZ decrement in microwave background DTP Colloquium, TIFR, 29 June 2010

  16. Cluster Physics Interplay - Example SZ scaling: DTP Colloquium, TIFR, 29 June 2010

  17. scaling mass fn Distribution of observable Probability of assigning obs mass-true mass Standard assumption: gaussian scatter in loglog plane Example - Lets talk about scatter… Scatter can boost signal, ex: Cl’s or n(z) Reason :shape of the mass function. Widens the range of possible masses for fixed value of the observable Include it by convolving the mass fn with distribution of the scatter DTP Colloquium, TIFR, 29 June 2010

  18. Pdf of s8 with priors on scatter Scatter and cosmology : Scatter – s8 degeneracy in dn/dz DTP Colloquium, TIFR, 29 June 2010

  19. Self-Calibration - A paradigm shift in cluster cosmology Use complimentary information from the survey itself e.g. the mass dependence of bias / spatial distribution Using the cluster power spectrum and P(k) oscillations Adding information from counts-in-cell 3. Shape of mass-function in redshift slices (Majumdar & Mohr, Lima & Hu) Unbiased parameter estimation with small error bars in the presence of systematics. This idea has now propagated to other fields in cosmology - Weak Lensing Galaxy Bias BAO Photo-z Non-gaussianity from LSS etc DTP Colloquium, TIFR, 29 June 2010

  20. Self Calibration using Cluster Power Spectrum Power spectrum of dark matter density fluctuations P(k) • Clusters are biased: 20,000 clusters comparable to ~5x105 galaxies • Turnover on large scales- “standard rod” calibrated by primary CMB fluctuations From redshift surveys, we will get P(k) for free ! DUET P(k) Unfortunately, only P(k) gives almost no constraints on `w’. Combined with CMB priors, one can constraint w ~ 25-30% Things become interesting when dn/dz and P(k) are Combined. SM & J.Mohr 2003 DTP Colloquium, TIFR, 29 June 2010

  21. Prospects for Self-Calibrating Cluster Survey… SM & J Mohr, 2003 DTP Colloquium, TIFR, 29 June 2010

  22. Some ideas on what to expect on DE … Xray - < 5-10% for eROSITA ~ 1% like from WFXT Similar constraints from optical with similar cluster numbers Ignore SZE for now! DTP Colloquium, TIFR, 29 June 2010

  23. `The Proof of the Pudding is in Eating’orReal Results from Real Survey(RCS1 and RCS2) DTP Colloquium, TIFR, 29 June 2010

  24. DTP Colloquium, TIFR, 29 June 2010

  25. We are in a little spot with recent SZE results… • Pre 2009 - • SPT/ACT surveys forecasted to yield 4-7clusters/deg • (Planck ~ 1000 to few 1000) • Post 2009 - • SPT/ACT finds 0.05-0.12 clusters/degsq • Also finds less SZ power in SZ Cl’s Implication - Cosmological constraints are washed out ! So, will doing cosmology with clusters become secondary science for these SZ surveys ? Need to do something More with these surveys!

  26. Our Options -1. Come up with new ideas for cluster surveys2a) Make progress with understanding of cluster physics (for cases wherecluster modeling cannot be avoided)2b) Make atleast a useful ‘working’ model of cluster3) Fall back on some old ideas of combining diff SZE outputs DTP Colloquium, TIFR, 29 June 2010

  27. Quick Thinking 1 - Change Survey Design Example - ACT - 2000 deg2 survey with tobs~107 s tobs 2000 deg2 ftime = fractional time spent on the smaller patch. 200deg2 1800 deg2 tS = ftimetobs tL = (1-ftime)tobs

  28. Magic of a ‘tiered’ survey (in numbers) …(from Satej’s talk) Single area survey (2000) deg2. factor of 4 improvement! better than mass follow-up BIG improvement! Wedding Cake survey (200+1800) deg2. Bottomline - A simple change of survey plan can do wonders

  29. XRay clusters Temp Sizes Common SZ clusters Overlapping areas for SZE+Xray surveys-An ensemble of dual detected clusters for free mock catalog of 430 clusters created from ACT/SPT+eROSITA for Nbeam=2 with minimum 20% errors in dA(z).

  30. dA from clusters ‘CAN BE LIKE’ dL from Sne !! 100 mass follow-up: 30-100 % error ACT/SPT dN/dz + dA(430) ACT/SPT dN/dz + SNe(307) ACT/SPT dN/dz only

  31. Use flux counts with SZ Cl to remove cluster uncertainties … Diego & SM DTP Colloquium, TIFR, 29 June 2010

  32. Higher - z and Larger Surveys -1. Completed Optical2. Proposed (and failed) Optical3. Upcoming and funded Xray 4. Proposed XRay DTP Colloquium, TIFR, 29 June 2010

  33. PI - G Wilson (USA) DTP Colloquium, TIFR, 29 June 2010

  34. …more DTP Colloquium, TIFR, 29 June 2010

  35. What about masses? - For the cluster in SpARCS SOUTH Vdisp = 1050 +/- 230 km/s M = 9.4 +/- 6.2 x 1014 Msun 5.7 x 1014 Msun (from scaling) z = 1.34 This cluster just should not exist !! Or maybe a sign of non-gaussianity We are working on it now. DTP Colloquium, TIFR, 29 June 2010

  36. DTP Colloquium, TIFR, 29 June 2010

  37. A comparison of survey volumes … SDSS: 10000 deg, z<0.5, Vol ~ 7 Gpc3 SPT/ACT : 2000- 4000deg, z=0.1 -1, Vol ~ 7-14 Gpc3 RCS2: 900 deg, z=0.2-0.9, Vol ~ 2.4 Gpc3 & SpARCS ~ 0.5 Gpc3 350 deg, z=1-2 Vol ~ 3.6 Gpc3 high-z survey having smaller area has same leverage due to Its higher volume! DTP Colloquium, TIFR, 29 June 2010

  38. Becoming more ambitious - More with Spitzer Proposed, for ~3000 hours (i. e., 4 months of Spitzer time) making it a legacy class survey: The Spitzer Legacy Extremely Wide Survey (SLEWS) PI: Jonathan Gardner (NASA) & Gillian Wilson (UCRiverside) (Multi country, multi supportive PI from other surveys, huge team Total members : 84 (with different backgrounds and expertise) Roughly 59 (USA), 24 (Europe + Japan), 1 (India) Basic coverage: 350 deg2 , 1< z < 2 Basic aim: a) To do clusters at high z b) To do quasars at z>6.5 when reionization is about to occur and there are probable stromgen spheres Passed initial stages but finally lost to a ExoPlanet Survey :-( DTP Colloquium, TIFR, 29 June 2010

  39. Into the ‘not too distant future’ - Wide Field Xray Telescope(Mission pushed ahead by R. Giacconi , 2010 Decadal Survey) If funded, this will be the mother of all cluster surveys DTP Colloquium, TIFR, 29 June 2010

  40. Forecast for WFXT - using N(z) + P(k) DTP Colloquium, TIFR, 29 June 2010

  41. with Cluster constraints on ‘generalised’ modified gravity models g = 0.55 for standard model (GR+LCDM) DTP Colloquium, TIFR, 29 June 2010

  42. Can India have a world class optical survey ???A comparison - I think its possible with a little effort !! Technology additions are easy and cheap. DTP Colloquium, TIFR, 29 June 2010

  43. Thanks Thanks also to Ravi Subrahmanyan, Biman Nath, Joe Mohr Martin White, Dick Bond, Wayne Hu, Nabila Aghanim, Joe Silk, Christoph Pfrommer, Nick Battaglia, Jon Sievers, Sudeep Das, Jose Diego,Bhuvnesh Jain, Howard Yee, Mike Gladders, Henk Hoekstra, Gillian Wilson, Adam Muzzin, Yen Ting Lin , Alexey Vikhlinin, Salman Habib, David Gilbank Zoltan Haiman + Satej Khedekar & Anya Chaudhuri. DTP Colloquium, TIFR, 29 June 2010

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